CN109118553A - Electrical impedance tomography content Boundary Reconstruction method based on geometric constraints - Google Patents

Electrical impedance tomography content Boundary Reconstruction method based on geometric constraints Download PDF

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CN109118553A
CN109118553A CN201810836856.0A CN201810836856A CN109118553A CN 109118553 A CN109118553 A CN 109118553A CN 201810836856 A CN201810836856 A CN 201810836856A CN 109118553 A CN109118553 A CN 109118553A
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任尚杰
王语
董峰
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Tianjin University
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    • G06T11/002D [Two Dimensional] image generation
    • G06T11/003Reconstruction from projections, e.g. tomography
    • G06T11/005Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
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Abstract

The electrical impedance tomography content Boundary Reconstruction method based on geometric constraints that the present invention relates to a kind of, comprising: 1) using the boundary of part arc length parameters x (s) characterization target contents;2) energy function based on residual error function and geometric constraints building shape inversion problem: 3) according to variation principle, the Optimal Boundary estimation x for minimizing energy function ε (x) meets Lagrange's equation;Sliding-model control is carried out to the variable in energy function, content boundary is characterized by series of discrete point [x (s1), x (s2) ..., x (sN)];4) Lagrange's equation is iteratively solved using semi-implicit method;5) by the sampled point in successive ignition back boundary estimated value can Step wise approximation target contents real border, realize content Boundary Reconstruction.

Description

Electrical impedance tomography content Boundary Reconstruction method based on geometric constraints
Technical field
The invention belongs to electrical impedance tomography technical fields, are related to a kind of content boundary based on geometric constraints Method for reconstructing.
Background technique
Electrical impedance tomography (Electrical Impedance Tomography, abbreviation EIT) is that one kind has non-invade Enter or the process visualization on-line monitoring technique of non-disturbance feature.It by being placed in the array-type sensor of sensitivity field to be measured, Apply electrical stimuli signal to target object field, and the electrical response letter of reflection sensitivity field internal conductance rate distributed intelligence can be obtained Number, and then realize the two-dimensional/three-dimensional visualization of dielectric distribution in field.The technology has portable, inexpensive and high time resolution The advantages that, there is wide application value in industry and biomedical aspect.However, the image reconstruction problem of EIT has seriously Non-linear and pathosis, this causes the spatial resolution of EIT lower, and vulnerable to noise jamming influence.For nonlinear solution Certainly method is usually to use iterative linearized or direct non-linear method.And pathosis can then pass through the benefit to prior information With being improved, common the way of restraint has smoothness constraint, sparse constraint etc..From other measurement patterns, such as ultrasonic measurement, calculate Hydrodynamics, dynamic data sequence etc., the prior information of acquisition also contribute to being promoted the spatial resolution of EIT.
EIT can be applied to the measurement of the bubble in such as Diagnosis of Breast Tumor, long-term monitoring of respiration and fluid field, The distribution of conductivity observed in domain in these applications is approximately piecewise constant, therefore the target of EIT is to rebuild limited be embedded in Simply connected subregion in homogeneous background conductivity, the content that these simply connected subregions are rebuild needed for being exactly.This segmentation Constrainted constants have the advantage for retaining content shape and enhancing content boundary resolution, therefore have attracted the field EIT Many concerns.
2007, S.Babaeizadeh et al. was published in " IEEE Transactions OnMedical Imaging (IEEE medical image processing) " volume 26, the 637-647 pages, entitled " Electrical impedance tomography for piecewise constant domains using boundary element shape-based inverse Solutions (the EIT Piecewise Constant number field inverse problem solution based on boundary element shape) ", it proposes a kind of using Piecewise Constant The content Boundary Reconstruction method of number constraint, this method parameterize the boundary of target contents, Zhi Houtong by one group of form factor It crosses minimum shape energy function and optimal content boundary estimation is calculated.It, should due to need to only rebuild the boundary of content Method is also referred to as the method for reconstructing based on shape, it reduces one-dimensional freedom degree compared to method for reconstructing pixel-based, because This content Boundary Reconstruction method holds out broad prospects in terms of the pathosis for improving EIT, the spatial resolution for promoting EIT.It is typical Boundary Reconstruction method there is H.Haddar in 2014 et al. to be published in " Complex Variables and Elliptic Equations (complex function and elliptic equation) " volume 59, the 863-882 pages, entitled " A conformal mapping Method in inverse obstacle scattering (the conformal transformation method in obstacle backscattering) " propose it is conformal Converter technique, F.Cakoni in 2012 et al. are published in " Inverse Problems (inverse problem) " volume 29,015005- Page 015027, entitled " Integral equation methods for the inverse obstacle problem with The generalized impedance boundary condition (integral equation of the inverse problem under Generalized impedance boundary conditions Method) " integration method that proposes, and certain methods based on boundary element method.
In the design of content Boundary Reconstruction method, key factor is the improvement to boundary parameterized model.General Boundary parameter model is divided into two kinds, global boundary model and local boundary model.Global boundary model, such as: 2007 S.Babaeizadeh et al. is published in that " IEEE Transactions On Medical Imaging is (at IEEE medical image Reason) " volume 26, the 637-647 pages, entitled " Electrical impedance tomography for piecewise Constant domains using boundary element shape-based inverse solutions (is based on side The EIT Piecewise Constant number field inverse problem solution of boundary's member shape) " the spherical harmonics model and D.K.Han in 1999 etc. that use People is published in " Journal ofComputational Physics (computational physics magazine) " volume 155, the 75-95 pages, inscribes For " A shape decomposition technique in electrical impedance tomography (electrical impedance Shape decomposition technology in tomography) " use Fourier model, the overall situation of object boundary can be embodied in reconstruction process Geometrical property, such as flatness.And local boundary model is usually defined in if some local geometric characteristics such as curvature etc., for example, S.Babaeizadeh in 2007 et al. is published in " IEEE Transactions On Medical Imaging (IEEE medicine shadow As processing) " volume 26, the 637-647 pages, entitled " Electrical impedance tomography for piecewise Constant domains using boundary element shape-based inverse solutions (is based on side The EIT Piecewise Constant number field inverse problem solution of boundary's member shape) " the B- Spline Model and M.M.Zhang in 2017 etc. that use People is published in " IEEE Sensors Journal (IEEE sensor magazine) " volume 17, the 8263-8270 pages, entitled 《Quantitative reconstruction ofthe exteriorboundary shape of metallic Inclusions using electrical capacitance tomography is (using capacitance chromatography imaging Quantitative Reconstruction gold Belong to field trash outer boundary shape) " use the model built on divergent boundary point.Two kinds of boundary models have respective excellent Gesture and limitation.On the one hand, since global boundary model contains the process of regularization, the shape based on global boundary model Method for reconstructing is more stable than the method based on local boundary model.On the other hand, since local boundary model is with higher Local deformation freedom degree, therefore local boundary model is more more flexible than global boundary model.For the shape of some complexity Such as concave shape can be more effectively carried out characterization using local boundary model.
Summary of the invention
For the present invention in content Boundary Reconstruction method, global and local parametrization boundary model cannot meet height simultaneously The problem of Boundary Reconstruction of stability and pinpoint accuracy, proposes a kind of content Boundary Reconstruction side based on geometric constraints Method, this method carries out regularization constraint to local boundary parameter model using geometric constraints, and devises new energy It minimizes equation and is used to restrained boundary Problems of Reconstruction, to reach the pathosis of improvement electrical impedance tomography problem while improve The purpose of Boundary Reconstruction stability and precision.Technical solution is as follows:
A kind of electrical impedance tomography content Boundary Reconstruction method based on geometric constraints, including the following steps:
1) using the boundary of part arc length parameters x (s) characterization target contents, wherein x ∈ Γ is indicated on object boundary Point set, s ∈ [0,1] are local arc length parameters, construct sensitivity matrix J and obtain boundary survey value vector U, using known to one group The measured value of distribution of conductivity U as the reference voltageref, surveyed boundary survey value U to be normalized, after normalization Boundary survey value vector is
2) energy function based on residual error function and geometric constraints building shape inversion problem:
Wherein, R (x) is residual error item, PΓIt (x) is geometric constraints item, U (x) is the content feature modeling by estimating And the estimated value of the boundary voltage gone out,Indicate square of 2- norm, symbol ' and " indicate x (s) to the first differential of s and two Rank differential,Indicating that the curve along object boundary Γ integrates, hyper parameter α and β are used to adjust the degree of geometric constraints, Distance change on power item constraint boundary between two consecutive points, for controlling the level of stretch on boundary, on stiffness term restrained boundary Disturbance, for controlling the curvature on boundary;
3) according to variation principle, the Optimal Boundary estimation x for minimizing energy function ε (x) meets following Lagrange Equation:
Wherein, symbol " " and " indicate x (s) to the quadravalence differential and second-order differential of s;M is the sum of boundary survey value;N is The exterior normal direction vector on content boundary;JiIndicate measured value UiAbout unit-boundary along exterior normal direction position at point x ∈ Γ The sensitivity of shifting, its calculation formula is:
Wherein, κ=σkbIt is content conductivityσkWith background media conductivityσbRatio;φ is calculated by direct problem Boundary electric potentials out;It is the differential operator along boundary exterior normal direction;It is the differential operator along boundary tangential direction;Ii =[I1,I2,…,IL]TIt is given exciting current vector, L is number of poles, MiBe from the measurement that excitation measurement strategies determine to Amount;
Sliding-model control is carried out to the variable in energy function, by series of discrete point [x (s1),x(s2),…,x(sN)] Content boundary is characterized, wherein N is the sum of boundary point, and the matrix form of Lagrange's equation is expressed as follows:
Wherein, N is N × N-dimensional diagonal matrix, and diagonal element is [n1n2,…,nN];J is M × N-dimensional sensitivity matrix; A is five diagonal band matrix of circulation:
Wherein, a=α/δ s2, b=β/δ s2, c=-a-4b, d=2a+6b;
4) Lagrange's equation is iteratively solved using semi-implicit method;
5) by the sampled point [x (s in successive ignition back boundary estimated value1),x(s2),…,x(sN)] can Step wise approximation mesh The real border of content is marked, is fitted to obtain the local arc length parameters x (s) for rebuilding content boundary later by discrete point, into And realize content Boundary Reconstruction.
Detailed description of the invention
Fig. 1 is the sensor structure used in specific embodiment and target contents to be reconstructed;
Fig. 2 is the schematic diagram of the content Boundary Reconstruction method based on geometric constraints;
Fig. 3 is the Boundary Reconstruction result under different conductivity contrasts and different signal-to-noise ratio that emulation obtains;
Fig. 4 be experiment obtain based under pixels approach and Method On Shape to single content rebuild comparing result;
Fig. 5 be experiment obtain based under pixels approach and Method On Shape to double contents rebuild comparing result.
Specific embodiment
The realization step of method involved in the present invention described in detail below, it is intended to it is described as the embodiment of the present invention, and Non- is the unique forms that the present invention realizes, can realize that the embodiment of identical structure and function also should include of the invention to other In range.
In a particular embodiment, shown in related EIT system sensor such as Fig. 1 (a), system includes 16 electrodes, It is even to be distributed in outside tested field domain.To simplify description, it is described in the present embodiment for single content Boundary Reconstruction.In mostly Inclusion Boundary Reconstruction can directly be extended by the method in the present embodiment.EIT system is using current excitation voltage measurement and excitation electricity The mode that pole does not measure, the boundary voltage under acquisition cycle motivation circulation measurement on each electrode constitute boundary survey value vector U.
The specific implementation flow of the embodiment mainly includes following steps:
(1) parametrization characterization target contents boundary
As shown in Fig. 1 (b), boundary Γ can be characterized as target contents to be reconstructed by a series of local arc length parameterizeds X (s), wherein x ∈ Γ indicates that the point set on object boundary, s ∈ [0,1] are local arc length parameters.
The mentioned method of the present invention is a kind of absolute imaging method, in order to reduce this method to model error and noise jamming Sensibility, a kind of method that the present invention proposes Virtual Calibration.It is used as using the measured value of one group of known conductivity distribution with reference to electricity Press Uref, surveyed boundary survey value U to be normalized.Boundary survey value vector after normalizationIt may be expressed as:
The purpose of Boundary Reconstruction method is exactly that the boundary of target contents to be reconstructed is estimated by boundary voltage measured value It is distributed x (s).
(2) energy function based on residual error function and geometric constraints building shape inversion problem
According to variation principle, solves Boundary Reconstruction problem and be equal to minimum residual error function.Different from common energy letter Number is constituted, present invention combination approximate error, and additionally constructs new energy function using geometric constraints, such as following formula institute Show:
ε (x)=R (x)+PΓ(x)
Wherein, R (x) is residual error item, PΓIt (x) is geometric constraints item.
Residual error item measures the approximate error between estimated voltage value and measurement voltage value:
WhereinFor boundary voltage measured value, U (x) is the content feature modeling by estimating and the boundary voltage that goes out is estimated Evaluation.Indicate square of 2- norm.Residual error item is changed by minimizing the difference between estimated voltage value and measurement voltage value Into the estimation being distributed to target contents boundary.But due to the pathosis of EIT problem, the process be highly prone to measurement noise and The influence of model error, so as to cause the estimated result of inaccuracy.
In order to improve problem above, the present invention uses geometric constraints as regularization term, for adding to energy function With constraint.Geometric constraints are illustrated by tension and rigidity:
Wherein, symbol ' and " indicate x (s) to the first differential and second-order differential of s,It indicates along object boundary Γ's Curve integral, hyper parameter α and β are used to adjust the degree of geometric constraints.On tension item constraint boundary between two consecutive points away from From variation, it is used to control the level of stretch on boundary.Disturbance on stiffness term restrained boundary, it is used to control the curvature on boundary.
(3) sliding-model control is carried out to the variable in energy function
Using shown in the present invention constrain in the case where, minimize energy function ε (x) be exactly find completely fitting measured value and Keep the optimal compromise between stability boundaris.According to variation principle, the Optimal Boundary for minimizing energy function ε (x) estimates x Meet following Lagrange's equation:
Wherein, symbol " " and " indicate x (s) to the quadravalence differential and second-order differential of s;M is the sum of boundary survey value;N is The exterior normal direction vector on content boundary;JiIndicate measured value UiAbout unit-boundary along exterior normal direction position at point x ∈ Γ The sensitivity of shifting, its calculation formula is:
Wherein, κ=σkbIt is content conductivityσkWith background media conductivityσbRatio;φ is calculated by direct problem Boundary electric potentials out;It is the differential operator along boundary exterior normal direction;It is the differential operator along boundary tangential direction;Ii =[I1,I2,…,IL]TIt is given exciting current vector, L is number of poles, MiBe from the measurement that excitation measurement strategies determine to Amount.
To solve the above Lagrange's equation, sliding-model control need to be carried out to variable.Using a constant interval δ s couple Local arc length parameters s is sampled, then content boundary to be reconstructed can be by series of discrete point [x (s1),x(s2),…,x(sN)] It indicates, wherein N is the sum of boundary point.In view of in above-mentioned Lagrange's equation each vector be it is independent and separable, can will Each vector is separated into the part x and y, uses ujIndicate x (sj) or y (sj), use njIndicate n (sj) x-component or y-component.Lagrange The matrix form of equation is expressed as follows:
Wherein, N is N × N-dimensional diagonal matrix, and diagonal element is [n1n2,…,nN];J is M × N-dimensional sensitivity matrix; A is five diagonal band matrix of circulation:
Wherein, a=α/δ s2, b=β/δ s2, c=-a-4b, d=2a+6b.In above-mentioned matrix equation, first item is by residual error Item R export, Section 2 is by geometric constraints item PΓExport.Sensitivity matrix J characterizes EIT measured value and content boundary The local linear relationship of variation.To prevent influence of the truncated error generated in calculating process to residual error item R and gradient r, at this Scaling processing is carried out to sensitivity matrix in embodiment, the sensitivity matrix after scaling is equal to J/max (J).
(4) Lagrange's equation is iteratively solved
The present invention iteratively solves the above Lagrange's equation using semi-implicit method.First, it is assumed that on the right of equation Constant and the equation left side item changes with iterative steps when item.Secondly, it is assumed that r is constant and is equal in iterative process each time In rt-1.Finally, it is assumed that matrix A is known in time t.
Such as lower boundary EVOLUTION EQUATION can be obtained according to above-mentioned hypothesis:
Wherein, δ t is time step.Thus the iteration form of the mentioned Boundary Reconstruction method of the present invention is derived:
Wherein S=δ tA+E is the filter by being calculated in geometrical constraint item, and E is unit matrix.
Fig. 2 illustrates the Computing Principle of the mentioned method of the present invention.In iterative process each time, the mentioned boundary weight of the present invention It builds the solver first step and optimum displacement gradient r is calculated by gradient descent method minimum residual error function Rt-1, second step later X is estimated using smoothing filter S adjustment boundary immediatelyt-1+δtrt-1.In an iterative process, hyper parameter α and β and sampling step length δ S is invariable.The selection of time step δ t need to comprehensively consider stability and convergence rate, rule of thumb, to realize light The selection of sliding and stable boundary approximate procedure, time step need to meet δ s2< δ tmax (Nr) < δ s.Iterative process is in residual error Sufficiently small or stopping when being approximately constant, therefore, stop condition setting are as follows:
Rt≤τ1or|Rt-Rt-1|/Rt-1≤τ2
Wherein, τ1It is the tolerance limit of residual error;τ2The tolerance of residual error variable quantity limits.Tolerance limit is selected according to trial-and-error method.
(5) content boundary profile is fitted
According to the above method, by the sampled point [x (s in successive ignition back boundary estimated value1),x(s2),…,x(sN)] Can Step wise approximation target contents real border, later by discrete point fitting can be realized with high stability and high-precision Content Boundary Reconstruction.
Result of implementation: test is emulated and tested to the embodiment above.Fig. 3 be emulation obtain in different conductivity Boundary Reconstruction under contrast and different signal-to-noise ratio as a result, Comparative result range be the conductivity contrast of 1.25-1000 with And joined 60dB, the Boundary Reconstruction result under 40dB and 20dB signal-to-noise ratio noise and noiseless, it can be seen that although rebuilding knot Fruit is deteriorated with the increase of noise, but the mentioned method of the present invention still has good noise immunity, under 20dB noise, is mentioned Method still can preferably reconstruct the position of target contents, size and shape.Meanwhile the noise immunity of mentioned method can lead to Raising conductivity contrast is crossed to improve.Fig. 4 be experiment obtain based under pixels approach and Method On Shape to single content weight The comparing result built, Comparative result NOSER algorithm imaging results, sparse imaging results based on L1 norm, TV regularization are calculated Method imaging results, and the imaging results of the Boundary Reconstruction method (abbreviation GCBR) based on geometric constraints proposed.It can To find out, the shape for the reconstruction content that method pixel-based can only be rough, wherein in NOSER algorithm can hardly identify The different shape of inclusion, and L1 and TV regularization can only substantially distinguish oval and triangle content, cannot distinguish between the rectangular and heart The content of shape.And mentioned method accurate can then reconstruct the geometry of target contents.Fig. 5 experiment obtains The comparing result that double contents are rebuild, it can be seen that compared to image rebuilding method pixel-based, the side GCBR proposed Method has better reconstructed results to non-circular content.

Claims (1)

1.一种基于几何形状约束的电阻抗层析成像内含物边界重建方法,包括下列步骤:1. A method for reconstructing the boundary of inclusions in electrical impedance tomography based on geometric constraints, comprising the following steps: 1)采用局部弧长参数x(s)表征目标内含物的边界,其中x∈Γ表示目标边界上的点集,s∈[0,1]为局部弧长参数,构建灵敏度矩阵J并获取边界测量值向量U,采用一组已知电导率分布的测量值作为参考电压Uref,用以对所测边界测量值U进行归一化,归一化后的边界测量值向量为 1) Use the local arc length parameter x(s) to represent the boundary of the target inclusions, where x∈Γ represents the point set on the target boundary, s∈[0,1] is the local arc length parameter, construct the sensitivity matrix J and obtain The boundary measurement value vector U uses a set of measurement values with known conductivity distribution as the reference voltage U ref to normalize the measured boundary measurement value U. The normalized boundary measurement value vector is 2)基于残差函数和几何形状约束构建形状反演问题的能量函数:2) Construct the energy function of the shape inversion problem based on the residual function and geometric shape constraints: 其中,R(x)为残差项,PΓ(x)为几何形状约束项,U(x)是由估计的内含物边界计算而出的边界电压的估计值,表示2-范数的平方,符号’和”表示x(s)对s的一阶微分和二阶微分,∮Γ·ds表示沿目标边界Γ的曲线积分,超参数α和β用来调整几何形状约束的程度,张力项约束边界上两相邻点间的距离变化,用来控制边界的拉伸程度,刚度项约束边界上的扰动,用来控制边界的曲率;where R(x) is the residual term, P Γ (x) is the geometry constraint term, U(x) is the estimated boundary voltage calculated from the estimated inclusion boundary, Represents the square of the 2-norm, the symbols 'and' represent the first and second derivative of x(s) with respect to s, ∮ Γ ds represents the curve integral along the target boundary Γ, and the hyperparameters α and β are used to adjust the geometry The degree of shape constraint, the change of the distance between two adjacent points on the boundary constrained by the tension term, is used to control the stretching degree of the boundary, and the stiffness term is used to constrain the disturbance on the boundary to control the curvature of the boundary; 3)根据变分法原理,使能量函数ε(x)最小化的最优边界估计x满足以下拉格朗日方程:3) According to the principle of variational method, the optimal boundary estimate x that minimizes the energy function ε(x) satisfies the following Lagrangian equation: 其中,符号””和”表示x(s)对s的四阶微分和二阶微分;M为边界测量值的总数;n为内含物边界的外法线方向向量;Ji表示测量值Ui关于单位边界在点x∈Γ处沿外法线方向位移的灵敏度,其计算公式为:Among them, the symbols "" and "represent the fourth-order and second-order differentials of x(s) against s; M is the total number of boundary measurements; n is the outer normal direction vector of the inclusion boundary; J i represents the measurement value U The sensitivity of i with respect to the displacement of the unit boundary at the point x∈Γ along the direction of the outer normal is calculated as: 其中,κ=σkb是内含物电导率σk与背景介质电导率σb的比值;φ是由正问题计算出的边界电势;▽n是沿边界外法线方向的微分算子;▽t是沿边界切线方向的微分算子;Ii=[I1,I2,…,IL]T是给定的激励电流向量,L为电极个数,Mi是由激励测量策略决定的测量向量;where κ = σ kb is the ratio of the conductivity of the inclusions σ k to the conductivity of the background medium σ b ; φ is the boundary potential calculated by the positive problem; ▽ n is the differential operator along the direction of the outer normal of the boundary ;▽ t is the differential operator along the tangent direction of the boundary; I i =[I 1 ,I 2 ,...,I L ] T is the given excitation current vector, L is the number of electrodes, M i is the measurement strategy determined by the excitation the determined measurement vector; 对能量函数中的变量进行离散化处理,由一系列离散点[x(s1),x(s2),…,x(sN)]表征内含物边界,其中N为边界点的总数,拉格朗日方程的矩阵形式表示如下:Discretize the variables in the energy function, and characterize the inclusion boundary by a series of discrete points [x(s 1 ),x(s 2 ),…,x(s N )], where N is the total number of boundary points , the matrix form of the Lagrange equation is as follows: 其中,N是N×N维的对角矩阵,对角元素为[n1n2,…,nN];J是M×N维的灵敏度矩阵;A为循环五对角带状矩阵:Among them, N is an N×N-dimensional diagonal matrix, and the diagonal elements are [n 1 n 2 ,…,n N ]; J is an M×N-dimensional sensitivity matrix; A is a cyclic five-diagonal band matrix: 其中,a=α/δs2,b=β/δs2,c=-a-4b,d=2a+6b;Wherein, a=α/δs 2 , b=β/δs 2 , c=-a-4b, d=2a+6b; 4)采用半隐式方法迭代求解拉格朗日方程;4) Iteratively solve the Lagrangian equation by semi-implicit method; 5)经过多次迭代后边界估计值上的采样点[x(s1),x(s2),…,x(sN)]可逐步逼近目标内含物的真实边界,之后经过离散点拟合得到重建内含物边界的局部弧长参数x(s),进而实现内含物边界重建。5) After several iterations, the sampling points [x(s 1 ), x(s 2 ),...,x(s N )] on the boundary estimation value can gradually approach the real boundary of the target inclusions, and then pass through discrete points The local arc length parameter x(s) of the reconstructed inclusion boundary is obtained by fitting, and then the reconstruction of the inclusion boundary is realized.
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CN109946388B (en) * 2019-02-20 2021-04-27 天津大学 Electrical/ultrasonic bimodal inclusion boundary reconstruction method based on statistical inversion
CN110827928A (en) * 2019-11-04 2020-02-21 曲阜师范大学 Method for constructing single-layer carbon fiber reinforced plastic conductivity model based on boundary element method
CN113052927A (en) * 2021-03-04 2021-06-29 河南师范大学 Imaging detection method for improving spatial resolution
CN113052927B (en) * 2021-03-04 2024-02-06 河南师范大学 Imaging detection method for improving spatial resolution

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